For the scrubbing of flue gases and, particularly, for the desulfurization of a flue gas by the treatment thereof with a scrubbing or absorptive liquid in a scrubbing column, it is known to provide the scrubbing column as a tower with a sump for collecting the scrubbing liquid, an absorption zone which may be free from baffles and packing and in which the gas is contacted with the liquid, and at least one nozzle plane above the absorption zone and provided with a manifold or distribution system for the scrubbing liquid, branch pipes and nozzles which dispense the scrubbing liquid into the gas.
The spray cones of the nozzles can overlap and the nozzles themselves may be connected to the branch pipes by intermediate pipe segments which run laterally of the branch pipes.
The gas can be passed in a uniform with the scrubbing liquid, i.e. in the same direction as the scrubbing liquid or in a counterflow to the scrubbing liquid. In the preferred state the gas passes upwardly while the nozzle plane is located at an upper portion of the scrubbing column.
Nozzle arrangements of the prior art encompass one or more nozzle planes, each of which has a distributor or manifold which is located in an axis of symmetry of the scrubbing column cross section and extends over the entire cross section of the scrubbing column. To the right and to the left branch lines are connected to the manifold, usually equidistantly so that these branch lines are disposed symmetrically. The connecting segments are likewise symmetrically disposed on the branch lines and have downwardly-turned ends which are formed with the nozzles. This nozzle distribution (see the U.K. Patent document 2 297 705) has a nozzle arrangement with overlapping spray cones and the nozzles distributed as much as possible uniformly over the cross section of the scrubbing column. The goal, of course, with these earlier systems is the greatest uniformity in the distribution of the spray over the cross sectional area of the column from a geometric view point.
It has been found from concentration measurements in the scrubbing gas stream above the nozzles that, in spite of a uniform distribution of the spray nozzles over the area of the scrubbing column cross section, there are locally higher toxic or noxious gas concentrations. The scrubbing gas stream appears to have tracks through the absorption zone which are not sufficiently contacted by the scrubbing liquid and in which noxious or toxic components, for example, sulfur-containing components, are not adequately removed by absorption.
As a consequence, the overall absorption efficiency of a scrubbing column is limited by the fact that there are local regions of greater and lesser scrubbing effectiveness. If a predetermined degree of absorption or absorption efficiency is not achieved, the length of the absorption zone must be increased and/or additional nozzle planes must be provided to increase the amount of the scrubbing liquid dispersed into the gas stream. Both of these expedients are expensive and are associated with increased operating gases for the additional pumping energy which is necessary. In many cases, moreover, existing scrubbing columns cannot be retrofit ted to achieve improved results.